System for modulating turbine blade tip clearance

ABSTRACT

A system for modulating turbine blade tip clearance is provided. The system may comprise an actuation control system having at least one actuator configured to modulate turbine blade tip clearance between a turbine blade tip and a blade outer air seal (BOAS). Each actuator may be coupled to the BOAS. Each actuator may comprise a solid-state motion amplification device such as a flextensional actuator. The actuators may be configured to move the BOAS in a radial direction from a first position to a second position to control tip clearance.

STATEMENT REGARDING GOVERNMENT RIGHTS

This disclosure was made with government support under contract No.NNX15AR27A awarded by the National Aeronautics and Space Administration(NASA). The government has certain rights in the disclosure.

FIELD

The present disclosure relates to gas turbine engines, and morespecifically, to a system for modulating blade tip clearances betweenturbine blades and blade outer air seal (BOAS) segments in gas turbineengines.

BACKGROUND

Gas turbine engines typically include a fan section, a compressorsection, a combustor section, and a turbine section. The compressorsection and/or the turbine section may include rotatable blades andstationary vanes. Blade outer air seals (BOAS) may be mounted within theengine casing, positioned in close proximity to the outermost tips ofthe rotatable blades. In response to acceleration of the gas turbineengine, the blade tips can expand outward due to increased heat andcentrifugal force at a faster rate than the case expands outward. Thetip clearance may be kept relatively large to avoid the blade tipsrubbing against the BOAS due to the rapid expansion of the bladerelative to the BOAS. The efficiency of the hot sections, and the gasturbine engine, may be undesirably affected by having a large tipclearance between the blade tips and the BOAS, such as, for example, dueto the hot gas leaking through the larger tip clearance.

SUMMARY

In various embodiments, an actuation control system is disclosed. Theactuation control system may comprise a actuator comprising an outershell radially opposite an inner shell. The actuation control system maycomprise a blade outer air seal (BOAS) segment coupled to the innershell of the actuator, wherein the BOAS segment is configured to movefrom a first position to a second position in response to an actuationfrom the actuator.

In various embodiments, the actuator may comprise a control wireconfigured to control the actuation of the actuator. The control wiremay comprise a shape memory alloy (SMA) wire configured to contract inresponse to receiving an electrical current, and wherein the contractingof the SMA wire controls the actuation of the actuator. The actuationcontrol system may further comprise a power supply having a controller,wherein the power supply is configured to transmit the electricalcurrent to the control wire in response to the controller determining atip clearance actuation event. In various embodiments, the actuator maybe configured to move the BOAS segment a distance of about 0.02 inches(0.508 mm) to about 0.05 inches (1.27 mm). In various embodiments, theactuation control system may further comprise a bias spring coupled tothe outer shell of the actuator. In various embodiments, the actuationcontrol system may further comprise a bias spring coupled to the innershell of the actuator between the coupling of the inner shell of theactuator and the BOAS segment.

In various embodiments, a turbine section of a gas turbine engine isdisclosed. The turbine section may comprise a turbine blade having ablade tip. The turbine section may comprise a blade outer air seal(BOAS). The turbine section may comprise an actuation control system.The actuation control system may comprise an actuator having an innershell radially opposite an outer shell, wherein the inner shell iscoupled to the BOAS and the outer shell is coupled to a radially innersurface of a turbine case, wherein the actuator is configured tomodulate a tip clearance between the blade tip and the BOAS.

In various embodiments, the actuator may be configured to move the BOASa distance of about 0.02 inches (0.508 mm) to about 0.05 inches (1.27mm) to control the tip clearance. In various embodiments, the actuatormay comprise a control wire configured to control the actuation of theactuator. The control wire may comprise a shape memory alloy (SMA) wireconfigured to contract in response to receiving an electrical current,and wherein the contraction of the SMA wire controls the actuation ofthe actuator. The turbine section may also comprise a power supplyhaving a controller, wherein the power supply is configured to transmitthe electrical current to the control wire in response to the controllerdetermining a tip clearance actuation event. In various embodiments, theturbine section may also comprise a bias spring coupled to the outershell of the actuator between the coupling of the outer shell of theactuator and the radially inner surface of the turbine case. In variousembodiments, the turbine section may also comprise a bias spring coupledto the inner shell of the actuator between the coupling of the innershell of the actuator and the BOAS.

In various embodiments, an actuation control system is disclosed. Theactuation control system may comprise a blade outer air seal (BOAS)segment having a first end opposite a second end; a first actuatorcoupled proximate the first end of the BOAS segment; and a secondactuator coupled proximate the second end of the BOAS segment. The firstactuator may be in electrical communication with the second actuator.The first actuator and the second actuator may be configured to move theBOAS segment from a first position to a second position in response toan actuation from the first actuator and the second actuator.

In various embodiments, the first actuator and the second actuator maycomprise a control wire having a shape memory alloy (SMA) wireconfigured to contract in response to receiving an electrical current,wherein the contraction of the SMA wire controls the actuation of eachactuator. The actuation control system may further comprise a powersupply having a controller, wherein the power supply is configured totransmit the electrical current to the control wire in response to thecontroller determining a tip clearance actuation event. In variousembodiments, the first actuator and the second actuator may beconfigured to move the BOAS segment a radial distance of about 0.02inches (0.508 mm) to about 0.05 inches (1.27 mm). In variousembodiments, the actuation control system may further comprise a biasspring coupled to at least one of a first outer shell of the firstactuator or a second outer shell of the second actuator. In variousembodiments, the actuation control system may further comprise a biasspring coupled to at least one of a first inner shell of the firstactuator between the coupling of the first actuator and the BOASsegment, or a second inner shell of the second actuator between thecoupling of the second actuator and the BOAS segment.

The forgoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated hereinotherwise. These features and elements as well as the operation of thedisclosed embodiments will become more apparent in light of thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the following illustrative figures. In thefollowing figures, like reference numbers refer to similar elements andsteps throughout the figures.

FIG. 1 illustrates a cross-section view of a gas turbine engine, inaccordance with various embodiments;

FIG. 2A illustrates a cross-section view of an actuation control systemhaving multiple actuators per a blade outer air seal (BOAS) segment in afirst position, in accordance with various embodiments;

FIG. 2B illustrates a cross-section view of the actuation control systemhaving multiple actuators per a BOAS segment in a second position, inaccordance with various embodiments;

FIG. 3A illustrates a cross-section view of an actuation control systemhaving one actuator per a BOAS segment in a first position, inaccordance with various embodiments;

FIG. 3B illustrates a cross-section view of an actuation control systemhaving one actuator per a BOAS segment in a second position, inaccordance with various embodiments;

FIG. 4A illustrates an exemplary actuator having a bias spring coupledto an outer shell of the actuator, in accordance with variousembodiments; and

FIG. 4B illustrates an exemplary actuator having a bias spring coupledto an inner shell of the actuator, in accordance with variousembodiments.

Elements and steps in the figures are illustrated for simplicity andclarity and have not necessarily been rendered according to anyparticular sequence. For example, steps that may be performedconcurrently or in different order are illustrated in the figures tohelp to improve understanding of embodiments of the present disclosure.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosures, it should be understood that other embodiments may berealized and that logical changes and adaptations in design andconstruction may be made in accordance with this disclosure and theteachings herein. Thus, the detailed description herein is presented forpurposes of illustration only and not of limitation.

The scope of the disclosure is defined by the appended claims and theirlegal equivalents rather than by merely the examples described. Forexample, the steps recited in any of the method or process descriptionsmay be executed in any order and are not necessarily limited to theorder presented. Furthermore, any reference to singular includes pluralembodiments, and any reference to more than one component or step mayinclude a singular embodiment or step. Also, any reference to attached,fixed, coupled, connected or the like may include permanent, removable,temporary, partial, full and/or any other possible attachment option.Additionally, any reference to without contact (or similar phrases) mayalso include reduced contact or minimal contact. Surface shading linesmay be used throughout the figures to denote different parts but notnecessarily to denote the same or different materials.

In various embodiments, and with reference to FIG. 1, a gas turbineengine 120 is disclosed. As used herein, “aft” refers to the directionassociated with a tail (e.g., the back end) of an aircraft, orgenerally, to the direction of exhaust of gas turbine engine 120. Asused herein, “forward” refers to the direction associated with a nose(e.g., the front end) of the aircraft, or generally, to the direction offlight or motion. An A-R-C axis has been included throughout the figuresto illustrate the axial (A), radial (R) and circumferential (C)directions. For clarity, axial axis A spans parallel to engine centrallongitudinal axis A-A′. As utilized herein, radially inward refers tothe negative R direction towards engine central longitudinal axis A-A′,and radially outward refers to the R direction away from engine centrallongitudinal axis A-A′.

Gas turbine engine 120 may comprise a two-spool turbofan that generallyincorporates a fan section 122, a compressor section 124, a combustorsection 126, and a turbine section 128. Gas turbine engine 120 may alsocomprise, for example, an augmenter section, and/or any other suitablesystem, section, or feature. In operation, fan section 122 may drive airalong a bypass flow-path B, while compressor section 124 may furtherdrive air along a core flow-path C for compression and communicationinto combustor section 126, before expansion through turbine section128. FIG. 1 provides a general understanding of the sections in a gasturbine engine, and is not intended to limit the disclosure. The presentdisclosure may extend to all types of applications and to all types ofturbine engines, including, for example, turbojets, turboshafts, andthree spool (plus fan) turbofans wherein an intermediate spool includesan intermediate pressure compressor (“IPC”) between a low pressurecompressor (“LPC”) and a high pressure compressor (“HPC”), and anintermediate pressure turbine (“IPT”) between the high pressure turbine(“HPT”) and the low pressure turbine (“LPT”).

In various embodiments, gas turbine engine 120 may comprise a low speedspool 130 and a high speed spool 132 mounted for rotation about anengine central longitudinal axis A-A′ relative to an engine staticstructure 136 via one or more bearing systems 138 (shown as, forexample, bearing system 138-1 and bearing system 138-2 in FIG. 1). Itshould be understood that various bearing systems 138 at variouslocations may alternatively or additionally be provided, including, forexample, bearing system 138, bearing system 138-1, and/or bearing system138-2.

In various embodiments, low speed spool 130 may comprise an inner shaft140 that interconnects a fan 142, a low pressure (or a first) compressorsection 144, and a low pressure (or a second) turbine section 146. Innershaft 140 may be connected to fan 142 through a geared architecture 148that can drive fan 142 at a lower speed than low speed spool 130. Gearedarchitecture 148 may comprise a gear assembly 160 enclosed within a gearhousing 162. Gear assembly 160 may couple inner shaft 140 to a rotatingfan structure. High speed spool 132 may comprise an outer shaft 150 thatinterconnects a high pressure compressor (“HPC”) 152 (e.g., a secondcompressor section) and high pressure (or a first) turbine section 154.A combustor 156 may be located between HPC 152 and high pressure turbine154. A mid-turbine frame 157 of engine static structure 136 may belocated generally between high pressure turbine 154 and low pressureturbine 146. Mid-turbine frame 157 may support one or more bearingsystems 138 in turbine section 128. Inner shaft 140 and outer shaft 150may be concentric and may rotate via bearing systems 138 about enginecentral longitudinal axis A-A′. As used herein, a “high pressure”compressor and/or turbine may experience a higher pressure than acorresponding “low pressure” compressor and/or turbine.

In various embodiments, the air along core airflow C may be compressedby low pressure compressor 144 and HPC 152, mixed and burned with fuelin combustor 156, and expanded over high pressure turbine 154 and lowpressure turbine 146. Mid-turbine frame 157 may comprise airfoils 159located in core airflow path C. Low pressure turbine 146 and highpressure turbine 154 may rotationally drive low speed spool 130 and highspeed spool 132, respectively, in response to the expansion.

In various embodiments, gas turbine engine 120 may comprise ahigh-bypass ratio geared aircraft engine. The bypass ratio of gasturbine engine 120 may also be greater than ten (10:1). Gearedarchitecture 148 may be an epicyclic gear train, such as a star gearsystem (sun gear in meshing engagement with a plurality of star gearssupported by a carrier and in meshing engagement with a ring gear) orother gear system. Geared architecture 148 may have a gear reductionratio of greater than about 2.3 and low pressure turbine 146 may have apressure ratio that is greater than about five (5). The diameter of fan142 may be significantly larger than that of the low pressure compressorsection 144, and the low pressure turbine 146 may have a pressure ratiothat is greater than about five (5:1). The pressure ratio of lowpressure turbine 146 is measured prior to inlet of low pressure turbine146 as related to the pressure at the outlet of low pressure turbine146. It should be understood, however, that the above parameters areexemplary of various embodiments of a suitable geared architectureengine and that the present disclosure contemplates other turbineengines including direct drive turbofans.

The next generation turbofan engines are designed for higher efficiencyand use higher pressure ratios and higher temperatures in high pressurecompressor 152 than are conventionally experienced. These higheroperating temperatures and pressure ratios create operating environmentsthat cause thermal loads that are higher than the thermal loadsconventionally experienced, which may shorten the operational life ofcurrent components.

In various embodiments, and with reference to FIGS. 2A and 2B, anactuation control system 200 is disclosed. Actuation control system 200may be located in any suitable location in gas turbine engine 120, suchas, for example, in high pressure turbine section 154. Actuation controlsystem 200 may be used to modulate a tip clearance 201 between bladetips 192 of turbine rotors and one or more blade outer air seal (BOAS)segments 190. Each BOAS segment 190 may be interconnected via a BOASmount 191. For example, actuation control system 200 may modulate tipclearance 201 in response to aircraft maneuvers and engine operatingparameters (e.g., engine idle, takeoff, cruise, etc.), and/or the like.A smaller tip clearance 201 may enable a more efficient gas turbineengine 120 by decreasing air loss in turbine section 154. Actuationcontrol system 200 may allow for modulation of tip clearances 201 duringengine operation, thus enabling smaller tip clearances 201 during higherheat operating cycles while also avoiding rubbing from blade tips 192.

Although actuation control system 200 is depicted as being utilized inhigh pressure turbine section 154, one skilled in the art will realizedthat an actuation control system similar to actuation control system 200may be used in low pressure turbine section 146, high pressurecompressor section 152, low pressure compressor section 144, and/or thelike, without departing from the scope of the disclosure. Moreover, asimilar actuation control system may also be used in a power turbinesection of a turboshaft, an intermediate pressure compressor of a threespool gas turbine engine, and/or an intermediate pressure turbine of athree spool gas turbine engine without departing from the scope of thedisclosure.

Actuation control system 200 may comprise one or more actuators 210configured to modulate the tip clearance 201. Each actuator 210 may beindependently controlled, controlled in pairs, and/or collectivelycontrolled. Each actuator 210 may be configured to cause a BOAS segment190 to move in a radially inward or radially outward direction tomodulate tip clearance 201. In that respect, each actuator 210 may beconfigured to move a BOAS segment 190 a distance of about 0.02 inches(0.508 mm) to about 0.05 inches (1.27 mm) (wherein about in this contextrefers only to +/−0.005 inches (0.127 mm)). Each actuator 210 may becoupled at an outer shell 211 to a radially inner surface of turbinecase 155, and at an inner shell 215 to a radially outer surface of BOASsegment 190. Actuation control system 200 may comprise any suitablenumber and/or configurations of actuators 210 capable of controllingmovement of a BOAS segment 190 in a radial direction. With reference toFIGS. 2A and 2B, in various embodiments, actuation control system 200may comprise multiple actuators 210 per a BOAS segment 190. For example,actuation control system 200 may comprise an actuator 210 at eachcircumferential end of BOAS segment 190. With reference to FIGS. 3A and3B, in various embodiments, actuation control system 300 may compriseone actuator 210 per a BOAS segment 190. For example, each actuator 210may be located in a position proximate the center of BOAS segment 190.

In various embodiments, and with reference to FIGS. 4A and 4B, actuator210 is depicted in greater detail. Actuator 210 may comprise anysuitable device, actuator, and/or the like capable of receiving an inputand generating an output to move a BOAS segment 190 in a radialdirection. For example, actuator 210 may comprise a flextensionalactuator, a thermal electric actuator, and/or any other suitablesolid-state motion amplification device capable of generating a force tomove the BOAS segment 190 in a radial direction.

In various embodiments, actuator 210 may comprise an outer shell 211coupled to an inner shell 215. Outer shell 211 may comprise a firstouter shell end 212 circumferentially opposite a second outer shell end213. Inner shell 215 may comprise a first inner shell end 216circumferentially opposite a second inner shell end 217. First outershell end 212 may be coupled to first inner shell end 216. Second outershell end 213 may be coupled to second inner shell end 217. Inner shell215 and outer shell 211 may comprise any suitable material capable ofallowing actuator 210 to flex in a radial direction, such as, forexample, a nickel alloy, titanium, carbon fiber, a nickel chromium alloy(such as that sold under the mark INCONEL, e.g., INCONEL 600, 617, 625,718, X-70, and the like) and/or any other suitable material.

In various embodiments, actuator 210 may comprise one or more controlwires 220. Actuator 210 may comprise any suitable and/or desired numberof control wires 220. For example, the number of control wires 220 maybe dependent on operational factors, desired actuation force fromactuator 210, and/or the like. Control wires 220 may be embedded betweenthe coupling of outer shell 211 and inner shell 215, and may extend in acircumferential direction through actuator 210. Control wires 220 mayalso be in electronic communication with control wires 220 from eachactuator 210 in actuation control system 200, such that all actuators210 in actuation control system 200 are in electronic communication witheach other (e.g., as depicted in FIG. 2A). For example, control wires220 may be connected in series, in parallel, in interdigital, and/or thelike. Control wires 220 may be configured to provide circumferentialtension to actuator 210 to control actuation of each actuator 210. Inthat respect, control wires 220 may comprise a shape memory alloy (SMA)wire 225 configured to contract when heated resistively and return toits original shape when cooled (e.g., by an airflow). SMA wire 225 maycomprise a nickel-titanium alloy, and/or any other suitable material.

In various embodiments, control wires 220 may comprise an insulatingmaterial 226, such as, for example, a ceramic bushing, and/or the like,configured to cover and insulate SMA wire 225. In that respect, controlwires 220 may comprise insulating material 226 between each actuator210, and SMA wire 225 with no insulating material 226 within eachactuator 210 (e.g., between the coupling of first outer shell end 212and first inner shell end 216 and the coupling of second outer shell end213 to second inner shell end 217).

In various embodiments, control wires 220 may comprise one or more metalbushings 228 configured to take a circumferential load and controlmovement of actuator 210 in a circumferential direction. For example,metal bushing 228 may be coupled to control wires 220 forward thecoupling of first outer shell end 212 and first inner shell end 216, anda metal bushing 228 may be coupled to control wires 220 aft the couplingof second outer shell end 213 to second inner shell end 217. In thatrespect, in response to SMA wire 225 contracting when receiving heat,metal bushings 228 may take the circumferential load and cause outershell 211 to move in a radially outward direction and inner shell 215 tomove in a radially inward direction (e.g., the coupling of first outershell end 212 and first inner shell end 216 and the coupling of secondouter shell end 213 to second inner shell end 217 may move in acircumferential direction towards each other, causing outer shell 211and inner shell 215 to move in a radial direction away from each other).In response to SMA wire 225 cooling, SMA wire 225 may expand, causingthe coupling of first outer shell end 212 and first inner shell end 216and the coupling of second outer shell end 213 to second inner shell end217 to move in a circumferential direction away from each other, thuscausing outer shell 211 and inner shell 215 to move in a radialdirection towards each other.

In various embodiments, actuator 210 may also comprise a bias spring230. Bias spring 230 may be configured to provide bias to actuator 210to push actuator 210 into a first position (or cold position), asdescribed further herein). Bias spring 230 may be in any suitableposition capable of providing bias to actuator 210. For example, asdepicted in FIG. 4A, bias spring 230 may be located on a radially outersurface of outer shell 211, between the coupling of outer shell 211 andturbine case 155. As another example, as depicted in FIG. 4B, biasspring 230 may also be located on a radially outer surface of innershell 215, between the coupling of inner shell 215 and BOAS segment 190.In various embodiments, bias spring 230 may also be located on each ofthe radially outer surface of inner shell 215 and the radially outersurface of outer shell 211 (e.g., two bias springs 230 in contact withactuator 210).

In various embodiments, and with reference again to FIGS. 2A and 2B,actuation control system 200 may comprise a power supply 205. Powersupply 205 may be in electronic communication with control wires 220 andmay be configured to provide an electrical current through control wires220. Power supply 205 may generate any suitable voltage, current, and/orpower to control wires 220. For example, in various embodiments, powersupply 205 may be expected to generate between five and ten Volts andbetween one and ten Amperes, direct current (DC).

In various embodiments, power supply 205 may incorporate and/or may bein logical communication with a controller 206 configured to control theoutput of electrical power from power supply 205. Controller 206 mayinclude logic configured to control output of electrical power, such as,for example, in response to determining a tip clearance actuation eventbased on engine operational factors such as gas turbine engine 120temperatures, high pressure turbine section 154 temperature, and/or thelike; engine state; and/or state of the aircraft (e.g., during takeoff,cruising altitude, landing, etc.). Controller 206 may include one ormore processors and/or one or more tangible, non-transitory memories andbe capable of implementing logic. Each processor can be a generalpurpose processor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof.

In various embodiments, controller 206 may comprise a processorconfigured to implement various logical operations in response toexecution of instructions, for example, instructions stored on anon-transitory, tangible, computer-readable medium. As used herein, theterm “non-transitory” is to be understood to remove only propagatingtransitory signals per se from the claim scope and does not relinquishrights to all standard computer-readable media that are not onlypropagating transitory signals per se. Stated another way, the meaningof the term “non-transitory computer-readable medium” and“non-transitory computer-readable storage medium” should be construed toexclude only those types of transitory computer-readable media whichwere found in In Re Nuijten to fall outside the scope of patentablesubject matter under 35 U.S.C. § 101.

In various embodiments, and with reference again to FIGS. 2A and 2B,actuation control system 200 having multiple actuators 210 per a BOASsegment 190 is depicted. With reference to FIG. 2A, actuators 210 aredepicted in a first position (or a hot position). In the first position,tip clearance 201 may comprise a first distance d1. First distance d1may comprise a radial distance between blade tip 192 and BOAS segment190. In the first position, first distance d1 may be configured toprovide tip clearance 201 for blade tip 192 to radially expand (e.g.,during a heating cycle). For example, first distance d1 may compriseabout 0.03 inches (0.762 mm) to about 0.035 inches (0.889 mm), about0.035 inches (0.889 mm) to about 0.04 inches (1.016 mm), about 0.04inches (1.016 mm) to about 0.045 inches (1.143 mm), and/or about 0.045inches (1.143 mm) to about 0.05 inches (1.27 mm) (wherein about in thiscontext refers only to +/−0.005 inches (0.127 mm)).

In various embodiments, and with reference to FIG. 2B, in response toreceiving an electrical current from power supply 205, actuators 210 maymove into a second position (or a cold position). For example, inresponse to receiving the electrical current, the SMA wire 225 withineach actuator 210 may contract causing actuator 210 to actuate in aradial direction away from turbine case 155. The actuation from actuator210 may cause a corresponding radial movement in BOAS segment 190. Inthe second position, tip clearance 201 may comprise a second distanced2. Second distance d2 may comprise a radial distance between blade tip192 and BOAS segment 190. Second distance d2 may be less than firstdistance d1. In the second position, second distance d2 may beconfigured to minimize tip clearance 201 between each BOAS segment 190and blade tip 192. For example, second distance d2 may comprise about0.005 inches (0.127 mm) to about 0.01 inches (0.254 mm), about 0.01inches (0.254 mm) to about 0.015 inches (0.381 mm), about 0.015 inches(0.0381 mm) to about 0.02 inches (0.508 mm), and/or about 0.02 inches(0.508 mm) to about 0.03 inches (0.762 mm) (wherein about in thiscontext refers only to +/−0.005 inches (0.127 mm)).

In response to blade tip 192 radially contracting during a cooling cycle(e.g., an air cooling cycle), power supply 205, via controller 206, maystop providing electrical current to control wires 220, allowing the SMAwires 225 in each actuator 210 to expand (e.g., as the SMA wires 225decrease in temperature). Expansion of the SMA wires 225, together witha force provide by bias spring 230, may allow each actuator 210 to moveback into the first position, increasing tip clearance 201 back to firstdistance d1.

In various embodiments, and with reference again to FIGS. 3A and 3B,actuation control system 300 having a single actuator 210 in operablecommunication with each BOAS segment 190 is depicted. With reference toFIG. 3A, actuators 210 are depicted in a first position (or a hotposition). In the first position, tip clearance 201 may comprise a firstdistance d1. First distance d1 may comprise a radial distance betweenblade tip 192 and BOAS segment 190. In the first position, firstdistance d1 may be configured to provide tip clearance 201 for blade tip192 to radially expand (e.g., during a heating cycle). For example,first distance d1 may comprise about 0.03 inches (0.762 mm) to about0.035 inches (0.889 mm), about 0.035 inches (0.889 mm) to about 0.04inches (1.016 mm), about 0.04 inches (1.016 mm) to about 0.045 inches(1.143 mm), and/or about 0.045 inches (1.143 mm) to about 0.05 inches(1.27 mm) (wherein about in this context refers only to +/−0.005 inches(0.127 mm)).

In various embodiments, and with reference to FIG. 3B, in response toreceiving an electrical current from power supply 205, actuators 210 maymove into a second position (or a cold position). For example, inresponse to receiving the electrical current, the SMA wire 225 withineach actuator 210 may contract causing actuator 210 to actuate in aradial direction away from turbine case 155. The actuation from actuator210 may cause a corresponding radial movement in BOAS segment 190. Inthe second position, tip clearance 201 may comprise a second distanced2. Second distance d2 may comprise a radial distance between blade tip192 and BOAS segment 190. Second distance d2 may be less than firstdistance d1. In the second position, second distance d2 may beconfigured to minimize tip clearance 201 between each BOAS segment 190and blade tip 192. For example, second distance d2 may comprise about0.005 inches (0.127 mm) to about 0.01 inches (0.254 mm), about 0.01inches (0.254 mm) to about 0.015 inches (0.381 mm), about 0.015 inches(0.0381 mm) to about 0.02 inches (0.508 mm), and/or about 0.02 inches(0.508 mm) to about 0.03 inches (0.762 mm) (wherein about in thiscontext refers only to +/−0.005 inches (0.127 mm)).

In response to blade tip 192 radially contracting during a cooling cycle(e.g., an air cooling cycle), power supply 205, via controller 206, maystop providing electrical current to control wires 220, allowing the SMAwires 225 in each actuator 210 to expand (e.g., as the SMA wires 225decrease in temperature). Expansion of the SMA wires 225, together witha force provided by a bias spring, may allow each actuator 210 to moveback into the first position, increasing tip clearance 201 back to firstdistance d1.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosures. The scope of the disclosures is accordinglyto be limited by nothing other than the appended claims and their legalequivalents, in which reference to an element in the singular is notintended to mean “one and only one” unless explicitly so stated, butrather “one or more.” Moreover, where a phrase similar to “at least oneof A, B, or C” is used in the claims, it is intended that the phrase beinterpreted to mean that A alone may be present in an embodiment, Balone may be present in an embodiment, C alone may be present in anembodiment, or that any combination of the elements A, B and C may bepresent in a single embodiment; for example, A and B, A and C, B and C,or A and B and C.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “various embodiments”, “oneembodiment”, “an embodiment”, “an example embodiment”, etc., indicatethat the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same embodiment.Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described. After reading the description, itwill be apparent to one skilled in the relevant art(s) how to implementthe disclosure in alternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element is intended to invoke 35 U.S.C. 112(f)unless the element is expressly recited using the phrase “means for.” Asused herein, the terms “comprises”, “comprising”, or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus.

What is claimed is:
 1. An actuation control system, comprising: anactuator; and a blade outer air seal (BOAS) segment coupled to an innershell of the actuator, wherein the BOAS segment is configured to movefrom a first position to a second position in response to an actuationfrom the actuator.
 2. The actuation control system of claim 1, whereinthe actuator comprises an outer shell radially opposite the inner shell,and a control wire configured to control the actuation of the actuator.3. The actuation control system of claim 2, wherein the control wirecomprises a shape memory alloy (SMA) wire configured to contract inresponse to receiving an electrical current, and wherein the contractingof the SMA wire controls the actuation of the actuator.
 4. The actuationcontrol system of claim 3, further comprising a power supply having acontroller, wherein the power supply is configured to transmit theelectrical current to the control wire in response to the controllerdetermining a tip clearance actuation event.
 5. The actuation controlsystem of claim 1, wherein the actuator is configured to move the BOASsegment a distance of about 0.02 inches (0.508 mm) to about 0.05 inches(1.27 mm).
 6. The actuation control system of claim 2, furthercomprising a bias spring coupled to the outer shell of the actuator. 7.The actuation control system of claim 1, further comprising a biasspring coupled to the inner shell of the actuator between the couplingof the inner shell of the actuator and the BOAS segment.
 8. A turbinesection of a gas turbine engine, comprising: a turbine blade having ablade tip; a blade outer air seal (BOAS); and an actuation controlsystem comprising an actuator having an inner shell, wherein the innershell is coupled to the BOAS, and wherein the actuator is configured tomodulate a tip clearance between the blade tip and the BOAS.
 9. Theturbine section of claim 8, wherein the actuator is configured to movethe BOAS a distance of about 0.02 inches (0.508 mm) to about 0.05 inches(1.27 mm) to control the tip clearance.
 10. The turbine section of claim8, wherein the actuator comprises an outer shell radially opposite theinner shell, wherein the outer shell is coupled to a radially innersurface of a turbine case.
 11. The turbine section of claim 8, whereinthe actuator comprises a control wire configured to control theactuation of the actuator, the control wire comprising a shape memoryalloy (SMA) wire configured to contract in response to receiving anelectrical current, and wherein the contraction of the SMA wire controlsthe actuation of the actuator.
 12. The turbine section of claim 11,further comprising a power supply having a controller, wherein the powersupply is configured to transmit the electrical current to the controlwire in response to the controller determining a tip clearance actuationevent.
 13. The turbine section of claim 10, further comprising a biasspring coupled to the outer shell of the actuator between the couplingof the outer shell of the actuator and the radially inner surface of theturbine case.
 14. The turbine section of claim 8, further comprising abias spring coupled to the inner shell of the actuator between thecoupling of the inner shell of the actuator and the BOAS.
 15. Anactuation control system, comprising: a blade outer air seal (BOAS)segment having a first end opposite a second end; a first actuatorcoupled proximate the first end of the BOAS segment; and a secondactuator coupled proximate the second end of the BOAS segment, whereinthe first actuator is in electrical communication with the secondactuator, and wherein the first actuator and the second actuator areconfigured to move the BOAS segment from a first position to a secondposition in response to an actuation from the first actuator and thesecond actuator.
 16. The actuation control system of claim 15, whereinthe first actuator and the second actuator comprise a control wirehaving a shape memory alloy (SMA) wire configured to contract inresponse to receiving an electrical current, wherein the contraction ofthe SMA wire controls the actuation of each actuator.
 17. The actuationcontrol system of claim 16, further comprising a power supply having acontroller, wherein the power supply is configured to transmit theelectrical current to the control wire in response to the controllerdetermining a tip clearance actuation event.
 18. The actuation controlsystem of claim 15, wherein the first actuator and the second actuatorare configured to move the BOAS segment a radial distance of about 0.02inches (0.508 mm) to about 0.05 inches (1.27 mm).
 19. The actuationcontrol system of claim 15, further comprising a bias spring coupled toat least one of a first outer shell of the first actuator or a secondouter shell of the second actuator.
 20. The actuation control system ofclaim 15, further comprising a bias spring coupled to at least one of afirst inner shell of the first actuator between the coupling of thefirst actuator and the BOAS segment, or a second inner shell of thesecond actuator between the coupling of the second actuator and the BOASsegment.